DE102021200088A1 - Air supply device for an aircraft fuel cell propulsion system - Google Patents

Abstract

The invention relates to an air supply device (10) and a method for supplying compressed air to at least one fuel cell (20) of an aircraft fuel cell drive, the aircraft fuel cell drive having an air supply device (10) with a compressor arrangement (11), wherein Ambient air is compressed by means of the compressor arrangement (11) and at least part of the compressed air is fed to the at least one fuel cell (20).

Description

The invention relates to an air supply device for an aircraft fuel cell drive with a compressor arrangement for supplying at least one fuel cell with compressed air and a method for supplying at least one fuel cell of an aircraft fuel cell drive with compressed air.

For their operation, fuel cells require, in addition to a fuel, an oxidizing agent, which in the case of fuel cells in aircraft engines is usually formed from air that is compressed in order to achieve a high power density. Since the pressure of the ambient air decreases with increasing flight altitude, an increase in the mass flow of the supplied air is necessary at higher flight altitudes in order to be able to supply a fuel cell with sufficiently compressed air largely independently of the flight altitude.

In addition to electrical energy, fuel cells also generate heat, which must be dissipated to prevent the fuel cells from overheating. For this purpose, during the flight phases, for example, propeller downwash (downwash air) and/or ram air is used, which is not available or not available to a sufficient extent, particularly on the ground and outside of a flight phase of an aircraft. Accordingly, during operation of the fuel cells outside of a flight phase of the aircraft, additional cooling of the fuel cells is required in order to dissipate sufficient heat from them.

Proceeding from this, it is an object of the present invention to propose an aircraft fuel cell drive with improved air supply and a method for supplying an aircraft fuel cell drive with compressed air. According to the invention, this is achieved by the teaching of the independent claims. Advantageous embodiments of the invention are the subject matter of the dependent claims.

In order to achieve the object, an air supply device for an aircraft fuel cell drive is proposed in a first aspect of the invention, with a compressor arrangement for supplying at least one fuel cell of the aircraft fuel cell drive with compressed air. The air supply device has at least one bypass device, by means of which part of the compressed air can be diverted at least temporarily to a cooling device of the at least one fuel cell.

A fuel cell of an aircraft fuel cell engine converts fuel and oxidant into electrical energy and a reaction product. An aircraft fuel cell drive usually has a large number of fuel cells which are arranged, for example, in the form of fuel cell stacks. Such a fuel cell arrangement, which correspondingly has at least one fuel cell, is simply referred to as “at least one fuel cell” within the scope of the description of the invention. Similar to a conventional turbomachine powered by kerosene, an aircraft fuel cell propulsion system requires compressed air as an oxidant in order to achieve high power density. The air supply device is used to supply the at least one fuel cell with compressed ambient air and, in addition to a compressor arrangement, also has the necessary lines, connections and valves for this purpose. The compressor arrangement has at least one correspondingly dimensioned compression device, by means of which the at least one fuel cell of the aircraft fuel cell drive can be supplied with a sufficient air mass flow for power generation even at high flight altitudes.

Such a compression device for compressing ambient air can be designed, for example, as a radial compressor. A compression device suitable for compressing air as an oxidizing agent for fuel cells is usually mounted in an oil-free manner, in particular with an air bearing or a hydrodynamic bearing. For example, a compression device of the compressor arrangement can also be designed in the form of a screw or turbo compressor.

The air supply device has at least one bypass device, by means of which part of the compressed air can be diverted at least temporarily to a cooling device of the fuel cell. In this way, in particular depending on the operating state of the fuel cell and/or the compressor arrangement, part of the air compressed by the compressor arrangement can be routed to a cooling device, which is provided for dissipating the excess heat generated by the at least one fuel cell, in particular to prevent overheating of the to avoid at least one fuel cell. The bypass device can be controlled or regulated, for example, so that the proportion of the compressed air guided through it to the cooling device can be adjusted. The bypass device directs the discharged air in particular directly to the cooling device of the at least one fuel cell. If the at least one fuel cell does not need to be cooled, the entire compressor output can be used to supply the fuel cell with oxidizing agent.

The bypass device can have a branching device arranged on the compressor arrangement, which in the form of a control or controllable valve is formed, which is arranged on an air duct for supplying the fuel cell with oxidizing agent. A portion of the air compressed by the compression arrangement can be branched off via the branching device. This is then - unlike the other part of the compressed air - not used as an oxidizing agent to supply the fuel cell, but to cool the fuel cell.

By means of the proposed air supply device, part of the compressed air can be discharged to a cooling device of the at least one fuel cell, in particular as required and therefore in particular temporarily. In operating phases in which the at least one fuel cell does not need to be cooled by the cooling device, the bypass can also be closed, which means that in particular all of the air compressed by the compression arrangement can be routed to the at least one fuel cell as an oxidizing agent. Correspondingly, the air mass flow guided through the bypass device to the cooling device of the at least one fuel cell can be supplied in a time-controlled and/or volume-controlled manner depending on its cooling requirement. For example, it is possible that no or only a small air mass flow is conducted through the bypass device to the cooling device in periods with no or only little cooling requirement, and a comparatively large air mass flow in periods with a high cooling requirement.

Such a cooling device can, for example, have at least one ejector (jet pump/air multiplexer) operated by the compressed air, which, in addition to cooling the fuel cell, can also be used in particular to support the overall cooling system, which is also used in particular to cool electric motors and frequency converters. The cooling device can also have air outlet nozzles, which are arranged in the area of a fuel cell and conduct cooling air in particular over the surface of the fuel cell housing. This housing or the cooling device can, in particular, also be equipped with cooling ribs that improve heat dissipation or other suitable elements through which cooling air can flow, such as cooling pipes or cooling ducts, or, for example, also suitable fans, air amplifiers or the like to improve heat dissipation by means of the cooling air from the at least one fuel cell exhibit.

The proposed air supply device allows part of the installed compressor capacity to be diverted for cooling, particularly on the ground and at low altitudes. Since there is a higher ambient air pressure near the ground, the corrected air mass flow through the compressor is smaller with the same delivery quantity to the fuel cell. With increasing flight altitude, the ambient air pressure decreases, which means that the required corrected air mass flow through the compressor increases with the same supply to the fuel cell, until finally the entire compressor capacity is required to supply the fuel cell. Since sufficient airflow is available in this flight phase and the fuel cell is operated at lower power, its cooling requirement decreases at the same time. In this way, the proposed air supply device for an aircraft fuel cell drive enables an advantageous interaction of a sufficient air mass flow for supplying the at least one fuel cell with sufficient oxidizing agent in the form of compressed air even at high altitudes and the provision of a sufficiently large cooling air flow for cooling the at least a fuel cell on the ground and in flight phases with less heat dissipation by the airborne wind, such as while waiting before the start of take-off. The performance of the fuel cell is high, while at the same time little or no cooling air from relative speed is available.

In one embodiment of the air supply device, the compressor arrangement has at least two compressor devices. The at least two compressor devices for compressing air can be arranged in parallel or in series, so that the at least two compressor devices form a single-stage or multi-stage compressor arrangement.

The compressor devices can be driven, for example, by an electric motor; in particular, at least two compressor devices arranged in parallel can also be driven by a common electric motor.

In a further embodiment of the air supply device, the compressor arrangement is designed in at least two stages. The air is guided from one compressor stage to the next, so that the degree of compression and thus the pressure or density of the compressed air increases with each compressor stage. With an increasing number of compressor stages, an increasing degree of compression of the air can be achieved. In this embodiment, too, each compression stage has one or more compression devices arranged in parallel. Comparatively small compressors with a low overall height can also be used advantageously in such a compressor arrangement.

In one embodiment of the air supply device, the bypass device is arranged after the first or after a second or after a further compressor stage. Due to the increasing compression of the air with each compression stage, the degree of compression of the air which is supplied to the cooling device of the fuel cell can be determined in the design of the air supply device by the arrangement of the bypass device or the air inlet of the bypass device. In this way, the cooling effect of the cooling device can be influenced by the arrangement of the bypass device. In particular, the positioning of the bypass device and thus a branch on the compressor arrangement determines the part of the compressed air that is routed to the at least one fuel cell and the part that is routed to the cooling device, and at the same time also influences the degree of compression of the compression arrangement downstream of the bypass device.

One embodiment of the air supply device has at least one air cooler for cooling the compressed air. Such an air cooler can be designed as a heat exchanger, for example. The temperature of the air guided through the air supply device increases as a result of the compression process, in particular as a result of the internal gas friction that occurs. Due to the higher temperature of the compressed air, the corrected air mass flow also increases, in particular in a subsequent compressor stage, and thus its power requirement.

The at least one air cooler can be used to cool the air in the air supply device, in particular after at least one compression stage, as a result of which the at least one fuel cell and/or the cooling device of the at least one fuel cell can be supplied with a higher air mass flow.

One embodiment of the air supply device has a water separator arranged after the at least one fuel cell for separating water from the exhaust gas of the at least one fuel cell. At least part of the separated water can be used to humidify the air which is fed to the at least one fuel cell as an oxidizing agent. The water serves to moisten the polymer electrolyte membrane of the fuel cell in order to increase its performance. Likewise, the humidification of the oxidizing agent also lowers the temperature of the air mass flow fed directly to the fuel cell. In order to operate the at least one fuel cell with an advantageous degree of efficiency, it is advantageous if the temperature of the oxidizing agent that is supplied to the at least one fuel cell is in a favorable temperature range. This temperature range depends on the type of fuel cell and is, for example, between 55°C and 95°C in the case of low-temperature fuel cells. Additionally separated water can be used for other devices of the aircraft fuel cell drive or the aircraft, such as for cooling devices. Separating water from the exhaust gas of the at least one fuel cell also serves to protect the environment, since this can reduce the formation of condensation strips in the atmosphere.

In one embodiment of the air supply device, it has a control device for controlling the devices of the air supply device. In addition to controlling, such a control device naturally also serves to regulate the air supply device with its elements and to integrate the air supply into the control of the aircraft fuel cell drive and the aircraft as a whole. Within the scope of the invention, the term “control” is also used for the corresponding “regulation”. In the context of the present invention, the control device of the air supply device serves in particular to coordinate the compression output of the compressor arrangement for supplying the at least one fuel cell with compressed air and thus for an adequate supply of oxidizing agent regardless of the flight altitude and for providing an adequate cooling air flow for cooling the at least one fuel cell in particular on the ground or in flight phases with cooling requirements.

• - Verdichten von Umgebungsluft mittels der Verdichteranordnung;
• - Zuführen wenigstens eines Teils der verdichteten Luft zur wenigstens einen Brennstoffzelle; und
• - Ableiten eines Teils der verdichteten Luft zum Kühlen der wenigsten einen Brennstoffzelle abhängig vom Kühlbedarf der wenigstens einen Brennstoffzelle.

In a second aspect, a method for supplying compressed air to at least one fuel cell of an aircraft fuel cell propulsion system is proposed in order to achieve the object, the aircraft fuel cell propulsion system having an air supply device with a compressor arrangement, characterized by the steps:

• - Compression of ambient air by means of the compressor assembly;
• - Supplying at least a portion of the compressed air to the at least one fuel cell; and
• - diverting a portion of the compressed air to cool the at least one fuel cell depending on the cooling needs of the at least one fuel cell.

An air supply device suitable for the application of the proposed method for an aircraft fuel cell propulsion system with a compressor arrangement can be designed in accordance with or a part of the preceding description and have at least some of the features described for this purpose.

In a first method step, ambient air is compressed in the compressor arrangement of the air supply device, in particular for supplying the compressed air as an oxidizing agent to the at least one fuel cell. The achieved degree of compression of the compressed air or the generated air mass flow is dependent on the ambient conditions of the aircraft fuel cell drive, in particular on the decreasing ambient pressure with increasing flight altitude. In order to achieve a sufficient degree of compression, the compressor arrangement can have a plurality of compressor devices and/or compressor stages, as described above, for example, in connection with the air supply device proposed in the first aspect of the invention.

In a second method step, at least part of the compressed air is supplied to the at least one fuel cell, where it is used as an oxidizing agent for generating power in the fuel cell. In order to be able to operate the at least one fuel cell with a high degree of efficiency, a sufficient air mass flow and thus also a sufficient degree of compression of the air supplied is required, as has already been described above for the proposed air supply device.

In a third method step, depending on the cooling requirement of the at least one fuel cell, part of the compressed air is discharged for cooling the at least one fuel cell. In this way, depending on the cooling requirement of the at least one fuel cell and in particular also on the operating state of the compressor arrangement, part of the air compressed by the compressor arrangement can be used to cool the at least one fuel cell, in particular to avoid overheating of the fuel cell. In phases in which the at least one fuel cell has a high requirement for oxidizing agent for its operation, but the cooling requirement is low, for example due to a strong wind, the discharge of part of the compressed air for cooling the at least one fuel cell can optionally also be interrupted at least temporarily .

To cool the at least one fuel cell with a portion of the compressed air, a cooling device arranged in particular in the area of the at least one fuel cell can be provided, which has one or more features of the cooling device described above in connection with the proposed air supply device.

To discharge the compressed air for cooling the at least one fuel cell, the air supply device can have at least one, in particular controllable, bypass device which is designed according to one or more features of the bypass device described above in connection with the proposed air supply device. The discharged air is thus - unlike the remaining part of the compressed air - not used as an oxidizing agent for supplying the fuel cell, but for cooling the at least one fuel cell.

The proposed method for supplying at least one fuel cell of an aircraft fuel cell drive with compressed air thus enables an advantageous interaction of a sufficient air mass flow for supplying the at least one fuel cell even at high altitudes with a sufficient supply of oxidizing agent in the form of compressed air and the provision of a sufficiently large Cooling air flow for cooling the at least one fuel cell in particular on the ground or in flight phases with less heat dissipation by the airborne wind. When the at least one fuel cell requires less air to generate power, for example at low altitudes or flight speeds or on the ground, the compressed air that is not required for generating power can be used to cool the at least one fuel cell.

One embodiment of the method for supplying compressed air to at least one fuel cell of an aircraft fuel cell drive system includes, as a further step, controlling the compression capacity of the compressor arrangement, in particular depending on the ambient conditions and/or the operating state of the at least one fuel cell. In this case, for example, the temperature of the at least one fuel cell, from which there is a need for the air mass flow required for cooling the at least one fuel cell, can be included in the control of the compression output.

One embodiment of the method for supplying compressed air to at least one fuel cell of an aircraft fuel cell drive system has a cooling of the compressed air as a further step. For this purpose, the air supply device has at least one air cooler, which is designed, for example, as a heat exchanger that can be. Such an air cooler can be arranged, for example, after at least one compressor stage, in order to cool the air that has been heated, in particular by the compression process, and thus to achieve a higher degree of compression. The cooling of the compressed air thus contributes to an increase in the air mass flow made available by the air supply device.

One embodiment of the method for supplying compressed air to at least one fuel cell of an aircraft fuel cell drive system has, as a further step, moistening of the compressed air by supplying water. As already described above, in particular the temperature of the air mass flow fed directly to the fuel cell can be reduced by the water. A lower oxidant temperature improves the efficiency of the at least one fuel cell. In particular, water that has been separated from the exhaust gas of the at least one fuel cell can be used for humidifying the compressed air.

• 1 eine schematische Darstellung einer beispielhaften erfindungsgemäßen Luftversorgungseinrichtung für einen Flugzeug-Brennstoffzellen-Antrieb;
• 2 eine schematische Darstellung einer weiteren beispielhaften erfindungsgemäßen Luftversorgungseinrichtung für einen Flugzeug-Brennstoffzellen-Antrieb;
• 3 eine schematische Darstellung noch einer weiteren beispielhaften erfindungsgemäßen Luftversorgungseinrichtung für einen Flugzeug-Brennstoffzellen-Antrieb; und
• 4 eine schematische Darstellung eines Ablaufdiagramms des erfindungsgemäßen Verfahrens zum Versorgen wenigstens einer Brennstoffzelle eines Flugzeug-Brennstoffzellen-Antriebs mit verdichteter Luft.

Further features, advantages and possible applications of the invention result from the following description in connection with the figures. It shows

• 1 a schematic representation of an exemplary air supply device according to the invention for an aircraft fuel cell drive;
• 2 a schematic representation of a further exemplary air supply device according to the invention for an aircraft fuel cell drive;
• 3 a schematic representation of yet another exemplary air supply device according to the invention for an aircraft fuel cell drive; and
• 4 a schematic representation of a flow chart of the method according to the invention for supplying at least one fuel cell of an aircraft fuel cell drive with compressed air.

1 shows a schematic representation of an exemplary air supply device 10 according to the invention for an aircraft fuel cell drive. The air supply device 10 has a compressor arrangement 11 for supplying the at least one fuel cell 20 with compressed air. The compressor arrangement 11 has a compressor device 12 which is driven by an electric motor 13 .

Ambient air is supplied to the air supply device 10 via an air inlet 2 , which air is then conducted through an air filter 3 to a compressor device 12 of the compressor arrangement 11 . The ambient air is compressed in the compressor device 12 and fed into a supply line 4 of the at least one fuel cell 20 .

A bypass device 16 is arranged on the supply line 4 of the air supply device 10 , by means of which part of the compressed air can be diverted at least temporarily to a cooling device 17 of the at least one fuel cell 20 . The bypass device 16 has a branching device 15 which is arranged after the compressor device 12 and thus after the first, since the only, compressor stage 21, by means of which a part of the compressed air can be diverted from the air flow. The compressed air can be routed via the bypass device 16 to the cooling device 17 , which is used there to cool the at least one fuel cell 20 .

After the compressor arrangement 21 of the air supply device 10 and before the at least one fuel cell 20, an air cooler 18 is arranged, which is used to cool the compressed air. The efficiency of the at least one fuel cell 20 can be increased with the help of the air cooler 18 since fuel cells are flown through by more air and thus more oxidizing agent when a cooler air mass flow flows through them, as a result of which a higher output can be generated.

An exhaust gas cooler 19 for cooling the exhaust gas flowing out of the fuel cell 20 is also arranged in the exhaust gas flow after the fuel cell 20 . On the one hand, this cooling process serves to recover heat and thus energy (recovery) and also reduces the formation of contrails during flight operations. In addition, the exhaust gas stream flowing out of the at least one fuel cell 20 is conducted via a water separator 31 which is arranged in the air stream after the fuel cell 20 and which separates water from the exhaust gas of the at least one fuel cell 20 . At least part of the water separated by the water separator 31 is routed to a humidifying device 32, which thus humidifies the compressed air flow supplied to the fuel cell 20 and in the process also lowers its temperature. Finally, the used ambient air is discharged to the environment via the air outlet 6 .

The air supply device 10 also has a control device 40 for controlling the devices of the air supply direction 10 up. As exemplary devices of the air supply device 10 controlled by the control device 40 are shown in FIG 1 embodiment shown, the compressor arrangement 21, the branching device 15, the humidifying device 32, the air cooler 18, the at least one fuel cell 20, the exhaust gas cooler 19 and the water separator 31 are shown connected to the control device 40 via signal lines 41 shown dotted.

2 shows a schematic representation of a further exemplary air supply device 10 according to the invention for an aircraft fuel cell drive. The air supply device 10 has a two-stage compressor arrangement 11 for supplying the at least one fuel cell 20 with compressed air. The first compressor stage 21 of the compressor arrangement 11 comprises two parallel compressor devices 12 which are driven by an electric motor 13 and the second compressor stage 22 of the compressor arrangement 11 has a compressor device 14 also driven by an electric motor 23 .

As in the execution of the 1 Ambient air is supplied to the air supply device 10 via an air inlet 2 and then passed through an air filter 3 to the first compressor stage 21 of the compressor arrangement 11 . The compressor devices 12 compress the ambient air and discharge it into a supply line 4 in parallel. An air cooler 28 is arranged in the supply line 4 and serves to cool the air compressed in the first compressor stage 21 . The cooled, compressed air is then further compressed by the second compressor stage 22 and guided on to the at least one fuel cell 20 .

In the exemplary in 2 illustrated embodiment of the air supply device 10, the branching device 15 of the bypass device 16 is arranged after one of the compressor devices 12 of the first compressor stage 21. In addition, the structure and function of the bypass device 16 in 2 the structure and function of the bypass device 16 from 1 .

As with the in 1 illustrated embodiment of the air supply device 10 are in the exhaust gas flow after the fuel cell 20 in 2 illustrated embodiment of the air supply device 10, an exhaust gas cooler 19, a water separator 31 and an air outlet 6 are arranged. It is analogous to the execution of the 1 at least a portion of the separated water is conducted to a humidifier 32 in order to humidify the compressed air stream supplied to the fuel cell 20 .

Also those in connection with 2 The air supply device 10 described has a control device 40 (not shown in the illustration) for controlling the devices of the air supply device 10 .

3 shows a schematic representation of yet another exemplary air supply device 10 according to the invention for an aircraft fuel cell drive, the structure of which largely corresponds to the structure in 2 illustrated air supply device 10 corresponds. The basic structure of the 2 and 3 Air supply devices 10 shown differs essentially by the arrangement of the bypass device 16 and the fact that the air supply device 10 of 3 has no air cooler 28 for cooling the compressed air in the first compressor stage 21 . Accordingly, the differences between the two versions are described below.

In the exemplary in 3 The illustrated embodiment of the air supply device 10 has the branching device 15 of the bypass device 16 arranged after the second compressor stage 22 in the supply line 4, so that in this embodiment more heavily compressed air is routed via the bypass device 16 to the cooling device 17, which is used there to cool the at least one fuel cell 20 serves.

Also those in connection with 3 The air supply device 10 described has a control device 40 (not shown in the illustration) for controlling the devices of the air supply device 10 .

4 shows a schematic representation of a flow chart of the method according to the invention for supplying at least one fuel cell 20 of an aircraft fuel cell drive with compressed air, the aircraft fuel cell drive having an air supply device 10 with a compressor arrangement 11 .

The method according to the invention has the following steps: In a first step a), ambient air is compressed by means of the compressor arrangement 11 and in a second step b) at least part of the compressed air is routed to the at least one fuel cell 20 . In a further step c), part of the compressed air for cooling the at least one fuel cell 20 is discharged as a function of the cooling requirement of the at least one fuel cell 20 .

In an optional embodiment of the method, in a step d) the compaction performance the compressor arrangement 11 controlled in particular depending on the ambient conditions and / or the operating state of the at least one fuel cell 20. In a further optional embodiment of the method, the compressed air is cooled in a step e) and in a further optional embodiment of the method the compressed air is humidified in a step f) by supplying water.

Reference List

2

air intake

3

air filter

4

supply line

6

air outlet

10

air supply device

11

compressor arrangement

12

compression device

13

electric motor

14

compression device

15

branching device

16

bypass device

17

cooling device

18

air cooler

19

exhaust gas cooler

20

fuel cell

21

first compressor stage

22

second compressor stage

23

electric motor

28

air cooler

31

water separator

32

humidification device

40

control device

41

signal lines

Claims (12)

Air supply device (10) for an aircraft fuel cell drive with a compressor arrangement (11) for supplying the at least one fuel cell (20) with compressed air, characterized by at least one bypass device (16) by means of which part of the compressed air is at least temporarily fed to a Cooling device (17) of the at least one fuel cell (20) can be derived. air supply device claim 1 , characterized in that the compressor arrangement (11) has at least two compressor devices (12, 14). air supply device claim 2 , characterized in that the compressor arrangement (11) is formed at least in two stages. Air supply device according to one of the preceding claims, characterized in that the bypass device (16) is arranged after the first or after a second or after a further compressor stage (21, 22). Air supply device according to one of the preceding claims, characterized by at least one air cooler (18, 28) for cooling the compressed air. Air supply device according to one of the preceding claims, characterized by a water separator (31) arranged after the at least one fuel cell (20) for separating water from the exhaust gas of the at least one fuel cell (20). Air supply device according to one of the preceding claims, characterized by a control device (40) for controlling the devices of the air supply device (10). Method for supplying at least one fuel cell (20) of an aircraft fuel cell drive with compressed air, the aircraft fuel cell drive having an air supply device (10) with a compressor arrangement (11), characterized by the steps: - compressing ambient air by means of compressor arrangement (11); - Supplying at least a portion of the compressed air to the at least one fuel cell (20); and - diverting a portion of the compressed air to cool the at least one fuel cell (20) depending on the cooling demand of the at least one fuel cell (20). Method for supplying an aircraft fuel cell drive with compressed air according to claim 8 , characterized by the further step: - controlling the compression capacity of the compressor arrangement (11), in particular depending on the ambient conditions and/or the operating state of the at least one fuel cell (20). Method for supplying an aircraft fuel cell drive with compressed air according to one of Claims 8 or 9 , known characterized by the further step: - Cooling of the compressed air. Method for supplying an aircraft fuel cell drive with compressed air according to one of Claims 8 until 10 , characterized by the further step: - Moistening the compressed air by supplying water. Aircraft fuel cell drive with at least one fuel cell (20) and an air supply device (10) according to at least one of Claims 1 until 7 is trained.

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